sponsored by STONE –––––––––––––––––––––––––––––– Lack of weep holes, uncollapsed mortar ridges may cause stone darkening in showers An ongoing issue with stone shower installations is that some- times stone showers mysteriously discolor or appear to not drain. There are various conditions and situations when this appears, and a range of explanations why this happens. Recently a NTCA Five-Star Contractor had a problem with a Calacatta marble tile shower, installed with 4” x 4” tileable drains, utilizing a topical waterproof mem- brane system. The contractor report- ed that the waterproofing used is not leaking, the slope is done according to code and the thin-set mortar was chosen appropriately for the instal- lation system and white marble. These topical membrane systems and drain assemblies are sometimes used in lieu of a traditional mortar bed shower pan application with weep holes. The contractor contacted the man- ufacturer rep as well as the tile sup- plier, asking, “We are wondering if the water infiltrates the white marble from the exposed edges around the drain enclosures, and because of its porous nature, and because of the waterproofing underneath, it is tak- ing much longer to dry.” Mark Heinlein, NTCA Training Director, enlisted the help of other By Lesley Goddin 88 TileLetter | November 2018